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Thiamine deficiency made my cat crazy!

VETERINARIAN SPECIALTY CASE STUDY

Thiamine, or vitamin B1, is a water-soluble vitamin that is required for carbohydrate metabolism.1 With a deficiency in this vitamin, normal energy metabolism is interrupted and the alternative anaerobic metabolism is stimulated which is detrimental to the brain.

1. Referral

Tilly, a 10-year-old spayed female domestic short hair cat, was referred to Animal Specialty Group on 12/13/2016 for evaluation and treatment for being unable to walk. Tilly was suddenly found earlier that day with all limbs splayed out and seeming to drag herself around by her front legs and crying out as if in pain. She was assessed quickly by her primary care veterinarian where bloodwork showed some mild liver enzyme evaluation and spinal and thoracic x-rays were unremarkable.

2. Examination

Tilly’s general physical examination was largely unremarkable aside from an increased body condition score of 7/9. Tilly’s neurologic examination revealed a positional vertical nystagmus (up and down abnormal eye movement), bilateral, wide, head excursions, a dull to inappropriate mentation, and severe vestibular ataxia with no ability to stand up right. These signs all pointed to a bilateral central vestibular (brain) neurologic problem.

T2 FLAIR transverse MRI images: Top – bilaterally symmetric T2 FLAIR hyper intensities in the area of the lateral geniculate nuclei. Bottom – bilaterally symmetric T2 FLAIR hyper intensities in the area of the caudal colliculi.

3. Diagnostics

As Tilly came in with recent full lab work and clear chest x-rays, Tilly was put under general anesthesia for a Brain MRI and spinal tap. Her brain MRI revealed symmetric T2 signal changes in the geniculate nuclei, caudal colliculi, and periaqueductal tissues. No masses or brain herniation was seen. Prior to anesthetic recovery Tilly had a spinal tap performed which ruled out any active inflammatory brain disease (encephalitis). Tilly the had blood submitted for a thiamine blood level, still pending, and a metabolic panel (organic aciduria screen) that was negative.

4. Diagnosis

Tilly was diagnosed with presumptive thiamine deficiency encephalopathy based on her characteristic clinical signs and brain MRI findings.

5. Treatment

Tilly was treated with supportive care and IV fluid therapy while hospitalized and started on twice daily subcutaneous injections of supplemental 100mg thiamine. She was also transitioned from a fish-based diet to a non-grain free, non-fish based cat food.

6. Discussion

Thiamine, or vitamin B1, is water-soluble vitamin that is required for carbohydrate metabolism.1 With a deficiency in this vitamin, normal energy metabolism is interrupted and the alternative anaerobic metabolism is stimulated which is detrimental to the brain.1

Cats, which are carnivores, require thiamine from the diet as they cannot appropriately synthesis or store this vitamin.2,3 Common causes include recent diet change to a grain free, fish based (especially raw), highly heated foods, or foods that have not been properly stored. 2,5,6 Primary gastrointestinal disease that prevents the body from absorbing thiamine will also lead to clinical signs.

Cats are more prone to thiamine deficiency than dogs, but both companion animal species can develop this disease.5 Clinical signs of deficiency can vary and can be very mild, but neurologic deficits often include vestibular (balance system) signs, visual deficits, mydriatic (large) and non-responsive pupils, trouble walking as well as seizures.1,5,6 MRI findings reported in cats with thiamine deficiency can include; bilaterally symmetric T1&T2 hyperintensities of the lateral geniculate nucleus, caudal colliculi, medial vestibular nuclei, and cerebellar nodulus without contrast enhancement.6

These findings appear to be distinctive for thiamine deficiency in cats however other metabolic/genetic encephalopathies are also known to cause bilaterally symmetric, non-contrast enhancing, brain lesions. Thiamine blood levels are not routinely run and therefore are only offered at a few specific labs in the country. They also tend to take several weeks to get a result so supplementation is recommended with or without this test. Most animals will respond rapidly to injectable or oral thiamine supplementation within days. 5,6

7. Recovery

Tilly showed marked improvement within 5 days and at her recheck examination she was up and walking around almost normally. She has been transitioned to an oral suspension of the thiamine supplementation and has persisted in her improvements. She may with time be able to be weaned of this supplementation since she is on a new, non-fish based, food, or may require life-long supplementation due to mild underlying malabsorptive issues. Repeat MRI images will show resolution of the originally identified lesion but is not always preformed due to cost and the need for a subsequent general anesthesia.